The aim of this research is to ascertain how the cells of the enamel organ function in bringing about the calcification of the maturing enamel. Since a model will be developed which will attempt to explain calcification at the cellular level, data will be referred to the ultrastructure of the cells and to their organization at the ultrastructural level. It has been shown by a number of investigators that maturation ameloblasts display two major structural configurations. During this program research, the arrangement of these two cell configurations on the maturing enamel surface has been mapped. Also during this program research, it has been shown that calcification occurs in patterns comparable to the arrangement of maturation ameloblasts. Thus, it appears that calcium entry is brought about by one cell configuration and calcium restriction by another. Once the cells responsible for calcification are identified, it becomes reasonable to characterize these cells quantitatively so that the results of experimental studies can be correctly interpreted. Experimental studies are planned to ascertain how long it takes for calcium to pass thorugh the enamel organ during the calcification of maturing enamel. Experiments are also planned to ascertain where the calcium is during this passage time.